256 lines
8.5 KiB
Plaintext
256 lines
8.5 KiB
Plaintext
[[modules-scripting-security]]
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=== Scripting and security
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You should never run Elasticsearch as the `root` user, as this would allow a
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script to access or do *anything* on your server, without limitations.
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You should not expose Elasticsearch directly to users, but instead have a
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proxy application inbetween. If you *do* intend to expose Elasticsearch
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directly to your users, then you have to decide whether you trust them enough
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to run scripts on your box or not, and apply the appropriate safety measures.
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[[enable-dynamic-scripting]]
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[float]
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=== Enabling dynamic scripting
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The `script.*` settings allow for <<security-script-fine,fine-grained>>
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control of which script languages (e.g `painless`) are allowed to
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run in which context ( e.g. `search`, `aggs`, `update`), and where the script
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source is allowed to come from (i.e. `inline`, `stored`, `file`).
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For instance, the following setting enables `stored` `update` scripts for
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`painless`:
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[source,yaml]
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----------------
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script.engine.painless.inline.update: true
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----------------
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Less fine-grained settings exist which allow you to enable or disable scripts
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for all sources, all languages, or all contexts. The following settings
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enable `inline` and `stored` scripts for all languages in all contexts:
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[source,yaml]
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-----------------------------------
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script.inline: true
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script.stored: true
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-----------------------------------
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WARNING: The above settings mean that anybody who can send requests to your
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Elasticsearch instance can run whatever scripts they choose! This is a
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security risk and may well lead to your Elasticsearch cluster being
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compromised.
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[[security-script-source]]
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[float]
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=== Script source settings
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Scripts may be enabled or disabled depending on their source: `inline`,
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`stored` in the cluster state, or from a `file` on each node in the cluster.
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Each of these settings takes one of these values:
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[horizontal]
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`false`:: Scripting is enabled.
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`true`:: Scripting is disabled.
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The default values are the following:
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[source,yaml]
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-----------------------------------
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script.inline: false
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script.stored: false
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script.file: true
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-----------------------------------
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NOTE: Global scripting settings affect the `mustache` scripting language.
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<<search-template,Search templates>> internally use the `mustache` language,
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and will still be enabled by default as the `mustache` engine is sandboxed,
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but they will be enabled/disabled according to fine-grained settings
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specified in `elasticsearch.yml`.
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[[security-script-context]]
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[float]
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=== Script context settings
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Scripting may also be enabled or disabled in different contexts in the
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Elasticsearch API. The supported contexts are:
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[horizontal]
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`aggs`:: Aggregations
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`search`:: Search api, Percolator API and Suggester API
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`update`:: Update api
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`plugin`:: Any plugin that makes use of scripts under the generic `plugin` category
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Plugins can also define custom operations that they use scripts for instead
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of using the generic `plugin` category. Those operations can be referred to
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in the following form: `${pluginName}_${operation}`.
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The following example disables scripting for `update` and `plugin` operations,
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regardless of the script source or language. Scripts can still be executed
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from sandboxed languages as part of `aggregations`, `search` and plugins
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execution though, as the above defaults still get applied.
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[source,yaml]
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-----------------------------------
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script.update: false
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script.plugin: false
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-----------------------------------
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[[security-script-fine]]
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[float]
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=== Fine-grained script settings
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First, the high-level script settings described above are applied in order
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(context settings have precedence over source settings). Then, fine-grained
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settings which include the script language take precedence over any high-level
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settings.
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Fine-grained settings have the form:
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[source,yaml]
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------------------------
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script.engine.{lang}.{source}.{context}: true|false
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------------------------
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And
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[source,yaml]
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------------------------
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script.engine.{lang}.{inline|file|stored}: true|false
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------------------------
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For example:
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[source,yaml]
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-----------------------------------
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script.inline: false <1>
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script.stored: false <1>
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script.file: false <1>
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script.engine.painless.inline: true <2>
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script.engine.painless.stored.search: true <3>
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script.engine.painless.stored.aggs: true <3>
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script.engine.mustache.stored.search: true <4>
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-----------------------------------
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<1> Disable all scripting from any source.
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<2> Allow inline Groovy scripts for all operations
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<3> Allow stored Groovy scripts to be used for search and aggregations.
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<4> Allow stored Mustache templates to be used for search.
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[[java-security-manager]]
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[float]
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=== Java Security Manager
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Elasticsearch runs with the https://docs.oracle.com/javase/tutorial/essential/environment/security.html[Java Security Manager]
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enabled by default. The security policy in Elasticsearch locks down the
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permissions granted to each class to the bare minimum required to operate.
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The benefit of doing this is that it severely limits the attack vectors
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available to a hacker.
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Restricting permissions is particularly important with scripting languages
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like Groovy which is designed to do anything that can be done
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in Java itself, including writing to the file system, opening sockets to
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remote servers, etc.
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[float]
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=== Script Classloader Whitelist
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Scripting languages are only allowed to load classes which appear in a
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hardcoded whitelist that can be found in
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https://github.com/elastic/elasticsearch/blob/{branch}/core/src/main/java/org/elasticsearch/script/ClassPermission.java[`org.elasticsearch.script.ClassPermission`].
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In a script, attempting to load a class that does not appear in the whitelist
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_may_ result in a `ClassNotFoundException`, for instance this script:
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[source,js]
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------------------------------
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GET _search
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{
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"script_fields": {
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"the_hour": {
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"script": "use(java.math.BigInteger); new BigInteger(1)"
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}
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}
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}
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------------------------------
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will return the following exception:
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[source,js]
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------------------------------
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{
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"reason": {
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"type": "script_exception",
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"reason": "failed to run inline script [use(java.math.BigInteger); new BigInteger(1)] using lang [painless]",
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"caused_by": {
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"type": "no_class_def_found_error",
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"reason": "java/math/BigInteger",
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"caused_by": {
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"type": "class_not_found_exception",
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"reason": "java.math.BigInteger"
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}
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}
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}
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}
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------------------------------
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[float]
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== Dealing with Java Security Manager issues
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If you encounter issues with the Java Security Manager, you have two options
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for resolving these issues:
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[float]
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=== Fix the security problem
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The safest and most secure long term solution is to change the code causing
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the security issue. We recognise that this may take time to do correctly and
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so we provide the following two alternatives.
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[float]
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=== Customising the classloader whitelist
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The classloader whitelist can be customised by tweaking the local Java
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Security Policy either:
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* system wide: `$JAVA_HOME/lib/security/java.policy`,
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* for just the `elasticsearch` user: `/home/elasticsearch/.java.policy`
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* by adding a system property to the <<jvm-options,jvm.options>> configuration: `-Djava.security.policy=someURL`, or
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* via the `ES_JAVA_OPTS` environment variable with `-Djava.security.policy=someURL`:
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+
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[source,js]
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---------------------------------
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export ES_JAVA_OPTS="${ES_JAVA_OPTS} -Djava.security.policy=file:///path/to/my.policy`
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./bin/elasticsearch
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---------------------------------
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Permissions may be granted at the class, package, or global level. For instance:
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[source,js]
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----------------------------------
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grant {
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permission org.elasticsearch.script.ClassPermission "java.util.Base64"; // allow class
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permission org.elasticsearch.script.ClassPermission "java.util.*"; // allow package
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permission org.elasticsearch.script.ClassPermission "*"; // allow all (disables filtering basically)
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};
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----------------------------------
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[TIP]
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======================================
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Before adding classes to the whitelist, consider the security impact that it
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will have on Elasticsearch. Do you really need an extra class or can your code
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be rewritten in a more secure way?
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It is quite possible that we have not whitelisted a generically useful and
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safe class. If you have a class that you think should be whitelisted by
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default, please open an issue on GitHub and we will consider the impact of
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doing so.
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======================================
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See http://docs.oracle.com/javase/7/docs/technotes/guides/security/PolicyFiles.html for more information.
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